This invention relates to a timing chain tensioner for use with a timing chain for driving an engine camshaft.
Conventional timing chain tensioners contain a plunger, which engages a timing chain, and a spring for biasing the plunger outward. The conventional timing chain tensioner is not provided with means for temporarily locking the plunger normally urged outward by the spring force, so that it is difficult to wind the timing chain around the sprockets in the course of engine assembling. In the case where a timing chain is set in place with a tensioner having no plunger locking means, the strong tension is applied to the chain by the plunger at all times so that the engaging of the chain with the sprockets and the mounting of the sprockets on the drive and driven shafts are very troublesome.
In an effort to solve the foregoing problems, a timing chain tensioner having means for temporarily locking the plunger has already been proposed. However, the proposal has nevertheless failed to offer a satisfactory solution.
The prior art tensioner still has a drawback in which the plunger cannot be rapidly introduced into the cylinder bore when the assembling of the tensioner is carried out, because the construction does not permit the air to leave the cylinder quickly as the plunger is led into the cylinder bore. The difficulty in the plunger insertion will be more greater when the plunger is inserted into the cylinder bore after the body portion of the tensioner is fixed to the wall of the engine block. After the body portion of the tensioner was mounted on the engine block, the cylinder bore is connected to the pressurized oil passage of engine lubricating system and the air trapped in the cylinder bore does not escape outside of the cylinder bore and further the air is compressed by the pressurized oil in the engine lubricating system, so that such the difficulty will be increased.